The preparation of formamide and N-substituted formamides from carbon monoxide and ammonia, primary or secondary amines is known to the art (U.S. Pat. Nos. 1,532,428 and 2,793,211). Widely varying reaction conditions have been reported, as has the use of various catalysts. Many of these processes give acceptable yields but require the carbon monoxide reactant to be free of substantial amounts of carbon dioxide, water (U.S. Pat. No. 2,866,822) and oxygen, (British Patent No. 823,778).
U.S. Pat. No. 3,781,352 discloses a process for producing formamides by mixing together ammonia or amine, carbon monoxide and oxygen in the presence of a catalyst, such as sodium methoxide, at a temperature of from about 20.degree. C. to about 260.degree. C. and at a pressure from about 10 to 200 atmospheres. The advantage of this process is that off-gases from basic oxygen furnaces in, for example, steel making plants can be advantageously used in the manufacture of formamide without first removing the oxygen.
In the preparation of N-alkylformamides, such as N,N-dimethylformamide, it has been the practice for some time to prepare these from the corresponding primary or secondary alkyl amine and carbon monoxide. Sodium in alcohol or sodium methoxide are typical catalysts. In European Patent Application No. 49,581, as well as U.S. Pat. No. 2,866,822, for example, N,N-dimethylformamide is produced from dimethylamine and carbon monoxide with an alkali metal methylate catalyst. Such preparations are often characterized by high pressures, high temperatures and long reaction times. Transition-metal catalysts are now often used to circumvent some of these problems. Kudo, Kiyoshi et al. in Chem. Lett. 1977, p. 1495, employ a palladium chloride catalyst and a base to prepare dimethylformamide from dimethylamine. In U.S. Pat. No. 3,446,842, N,N-dimethylformamide is produced by carbonylating a mixture of ammonia and methylamine in the presence of certain cobalt-containing catalysts. Similarly in German Patent No. 863,800, contacting of trimethylamine and carbon monoxide in the presence of a supported catalyst comprising mixtures of oxides and magnesium, thorium and cobalt, produces dimethylformamide.
U.S. Pat. No. 2,793,211 teaches the preparation of N-alkylformamides from the corresponding alkylamine and carbon monoxide under mild temperatures using choline and the like as a catalyst.
In contrast to related art, we disclose a new preparation route to N-alkylsubstituted formamides, such as N,N-dimethylformamide or N-methylformamide, which employs only ammonia and synthesis gas as reactants (eq. 1). ##STR1##
The new process of this invention allows the synthesis of N,N-dimethylformamide and N-methylformamide without the need for a methylamine, dimethylamine, trimethylamine or other alkyl-substituted amine coreactant.
Disadvantages of the prior processes for preparing N,N-dimethylformamide and N-methylformamide include the necessity for providing certain alkylamine coreactants. It would be a significant advantage to devise a new synthetic route to dimethylformamide from the low cost building blocks ammonia and synthesis gas.